ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

3aEA2. Evaluation of a computationally assisted low-frequency calibration
technique in an acoustic tank.

Claude A. LeDoux

Regina M. DuBord

Naval Undersea Warfare Ctr., Div. Newport, Newport, RI 02840

Acoustic tank calibration of transducers using low-frequency pulsed
sinusoidal inputs (below 500 Hz) in water has generally been impossible, due to
strong, variable signal reflections from the tank walls and air--water interface
that corrupt measurements before the transducer response reaches steady state.
Since the large tank size needed to overcome this difficulty is impractical, a
computational scheme has been investigated for predicting these steady-state
responses. Specifically, Prony's method, applied to the echo-free portion of a
response signal, has been employed to generate a mathematical signal model which
theoretically can be used to extrapolate the response to any later time, as
suggested by Beatty et al. [J. Acoust. Soc. Am. 63, 1782--1794 (1978)]. An
experimental assessment of this approach, performed in the Naval Undersea
Warfare Center acoustic tank, as well as experimental justification of its
validity, will be presented.